Method of mounting semiconductor chip

ABSTRACT

A method of mounting a semiconductor chip in which an IC chip is mounted by filling a gap between the chip and a substrate with adhesive which functions as an underfill. The fillet of the underfill is made to have a preferable shape. To accomplish this, a head IC chip provided with bumps is placed on a suspension that is covered with the underfill adhesive and is provided with pads. A bonding tool presses the head IC chip and applies ultrasonic oscillation to the head IC chip, so that the bumps are properly bonded to the pads. When the head IC chip is pressed and subjected to ultrasonic oscillation, the ultraviolet rays  108  are emitted so as to harden the peripheral portion  151   a  of the adhesive  151  spread out between the head IC chip  11  and the suspension  12.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method of mounting asemiconductor chip and an apparatus for mounting a semiconductor chip.

The method of mounting a semiconductor chip can be applied to mountingof a head IC chip 11 of a hard disk device 10 to a suspension 12, asshown in FIGS. 1A and 1B, or to mounting of an IC chip 31 of a printedcircuit board unit 30 to a substrate 32, as shown in FIGS. 3A to 3C.

As shown in FIGS. 1A and 1B, the hard disk device 10 has a hard disk 16that rotates at high speed in a hermetically sealed housing 15, and ahead slider assembly 19 attached to the top end of an arm 18. The headslider assembly 19 comprises a head slider 20 and the head IC chip 11mounted on the suspension 12, as shown in FIG. 2. The head slider 20 hasa magnetic head 21 formed by a thin film forming technique. The head ICchip 11 fimctions to control the magnetic head 21 by amplifying a weaksignal read by the magnetic head 21, for instance. As shown in theenlarged view in FIG. 2, the head IC chip 11 has Au bumps 22 on itslower surface joined to Au pads 24 at the edge of a wiring pattern 23.

The printed circuit board unit 30 comprises a multi chip module 36provided with a heat sink, a memory socket 38, and an I/O connector 39,all mounted on a mother board 35, as shown in FIG. 3A. The multi chipmodule 36 has a plurality of IC chips 31 mounted on the substrate 32, asshown in FIG. 3B. The head IC chip 31 has Au bumps 42 on its lowersurface bonded to Au pads 43 formed on the substrate 32. The head ICchip 31 is also bonded onto the substrate 32 by underfill 44.

2. Description of the Related Art

FIGS. 4A to 4C illustrate a method of producing a conventional headslider assembly. The head IC chip 11 has Au bumps 51 on its lowersurface. The suspension 12 has Au pads 61 on its upper surface. Thishead slider assembly is manufactured in the following manner.

First, the suspension 12 is fixed onto a stage 70. A predeterminedamount of insulating adhesive 71 functioning as “underfill” is thenapplied to the upper surface of the suspension 12, using a precisiondispenser (not shown). The head IC chip 11 is picked up by vacuumsuction of a tool 75 having a suction hole 76, and is moved onto thesuspension 12. The tool 75 then presses the head IC chip 11 by a forceF, and ultrasonic vibration of several μm amplitude is applied to thehead IC chip 11 for several seconds, as indicated by an arrow B. Bydoing so, the Au bumps 51 are bonded to the Au pads 61. The vacuumsuction of the tool 75 is then stopped, so that the tool 75 is separatedfrom the head IC chip 11. The suspension 12 is then moved to a heatingfurnace 80, so that the adhesive 71 is hardened by heat. Here, underfill72 is formed, and the head IC chip 11 is bonded to the suspension 12 bythe underfill 72. Thus, the head slider assembly 19 is completed.

The above method of producing a conventional head slider assemblyexhibits at least the following disadvantages:

1. The shape of the fillet of the underfill is unstable.

The adhesive 71 functioning as the underfill is circular on thesuspension 60, as indicated by a two-dot chain line in FIG. 5A. As thetool 75 presses the head IC chip 11, the adhesive 71 is pressed by thelower surface of the head IC chip 11, and is radially spread out. Thespread adhesive 71 reaches the periphery of the lower surface of thehead IC chip 11, and forms a fillet 90. The shape of the fillet 90 isdetermined by the spread state of the adhesive 71 to functions as theunderfill. The spread state of the adhesive 71 varies with the appliedamount and the applied position of the adhesive 71. Depending on thesituation, the adhesive 71 may significantly overflow on the uppersurface of the suspension 12, as indicated by reference numeral 91 inFIGS. 5A and 5B.

As the hard disk device becomes smaller, the width W1 of the suspension12 becomes smaller. On the other hand, as more functions are added, thehead IC chip 11 becomes larger in the direction of L1 shown in FIG. 5A.Accordingly, the extra portion 92 outside the mounted head IC chip 11 onthe suspension 12 becomes smaller in a width W2. Furthermore, the largeamount of overflow of the adhesive has an adverse effect on the on thefloating characteristic of the head slider 20 with respect to a harddisk.

As for the multi-chip module 36 shown in FIGS. 3A to 3B, the largeamount of overflow of the adhesive on the upper surface of the substrate32 often hinders the mounting of other components.

2. The overflowing adhesive sticks to the tool 75.

Depending on the applied amount and the applied position of the adhesive71, the adhesive 71 overflows onto the upper surface of the head IC chip11 and sticks to the top end of the tool 75, as indicated by referencenumeral 93 in FIGS. 6A and 6B.

When the adhesive 71 sticks to the top end of the tool 75, the suctionoperation of the tool 75 becomes unstable. Therefore, the top end of thetool 75 requires cleaning often. However, it is troublesome to clean thetop end of the tool 75 every time the mounting of one head IC chip 11 iscompleted.

The applied adhesive 71 is applied in a circular pattern and spreadsradially, when seen from above. Accordingly, the adhesive 71 overflowsfrom the sides of the head IC chip 11, and reaches the upper surface ofthe head IC chip 11.

3. The transmission rate of ultrasonic waves from the tool 75 to thehead IC chip 11 is low.

As shown in FIG. 4B, the tool 75 is brought into contact directly withthe head IC chip 11. The tool 75 is made of stainless steel, and thehead IC chip 11 is made of silicon. The friction coefficient μ1 betweenthe tool 75 and the IC chip 11 is in the range of 0.5 to 0.7, which isrelatively low. Accordingly, the transmission rate of ultrasonic wavesfrom the tool 75 to the head IC chip 11 is low, and the bonding of theAu bumps 51 to the Au pads 61 requires a long period of time.

4. The head IC chip often deviates at the time of mounting, and thedeviation results in defective mounting.

As shown in FIG. 4B, the tool 75 and the head IC chip 11 are in contactwith each other.

Due to the slight orientation of the end surface 75 a of the tool 75,the head IC chip 11 slightly deviates from the initial position shown inFIG. 7A in one direction of the ultrasonic oscillation (in the X1direction, for instance) every time the tool 75 ultrasonicallyoscillates. Depending on the situation, the Au bumps 51 might slip offthe Au pads 61, as shown in FIG. 7B, resulting in defective bonding.

In the multi-chip module 36 shown in FIGS. 3A to 3C, the pads formed onthe substrate 32 each have a rectangular shape, as indicated byreference numeral 43A in FIG. 8. However, the longitudinal direction ofthe horizontally aligned pads 43A in FIG. 8 is equivalent to the widthdirection of the vertically aligned pads 43A in FIG. 8. Accordingly, thepads on the substrate 32 are not always effective in preventing the headIC chip 11 from deviating when the tool 75 ultrasonically oscillates.

In view of this, the present invention is directed to providing asemiconductor chip mounting method and device, in which the aboveproblems are eliminated.

SUMMARY OF THE INVENTION

To solve the problems mentioned above, the present invention provides amethod of mounting a semiconductor chip, comprising the steps of:

bonding bumps formed on the semiconductor chip to pads formed on asubstrate by pressing the semiconductor chip, with insulating adhesivebeing interposed between the semiconductor chip and the substrate; and

hardening the insulating adhesive spread out between the semiconductorchip and the substrate,

wherein the bonding step includes the step of hardening a peripheralportion of the insulating adhesive spread out between the semiconductorchip and the substrate.

Since the peripheral portion of the insulating adhesive spread outbetween the semiconductor chip and the substrate while the semiconductorchip is pressed, a large amount of overflow of the insulating adhesivecan be prevented. Thus, the fillet of the underfill can be formed in apreferable shape.

In the above method, the bonding step may further include the step ofapplying ultrasonic oscillation to the semiconductor chip so that thebumps formed on the semiconductor chip are bonded to the pads formed onthe substrate.

Since the insulating adhesive does not overflow in large volume, theinsulating adhesive can be prevented from entering the contact spacebetween the bonding tool and the semiconductor chip. Thus, thepreferable contact condition can be maintained.

In the above method, the peripheral portion of the insulating adhesivemay be hardened by either light or heat.

With light or heat, the peripheral portion of the insulating adhesivespread out between the semiconductor chip and the substrate can bequickly and stably hardened.

The present invention also provides a semiconductor chip mounting devicethat comprises a mechanism for pressing a semiconductor chip while aninsulating adhesive is interposed between the semiconductor chipprovided with bumps and a substrate provided with pads, and mounts thesemiconductor chip on the substrate by bonding the bumps to the pads,

the device further comprising a peripheral portion hardening unit thathardens a peripheral portion of the insulating adhesive exposed from aperiphery of the semiconductor chip while the semiconductor chip ispressed.

Since the peripheral portion of the insulating adhesive spread outbetween the semiconductor chip and the substrate while the semiconductorchip is pressed, the insulating adhesive can be prevented fromoverflowing in large volume. Thus, the fillet of the underfill can beformed in a preferable shape.

The above semiconductor chip mounting device also comprises anultrasonic oscillator that ultrasonically bonds the bumps to the pads.

Since the insulating adhesive does not overflow in large volume, theinsulating adhesive can be prevented from entering the contact spacebetween the bonding tool, which transmits ultrasonic oscillation, andthe semiconductor chip. Thus, a preferable contact condition can bemaintained.

In the above semiconductor chip mounting device, the peripheral portionhardening unit is either a light supplying unit or a heat supplyingunit.

With the light supplying unit or the heat supplying unit, the peripheralportion of the insulating adhesive which spreads out between thesemiconductor chip and the substrate can be quickly and stably hardened.

The present invention also provides a semiconductor chip mounting devicethat comprises a bonding tool that presses a semiconductor chip while aninsulating adhesive is interposed between the semiconductor chipprovided with bumps and a substrate provided with pads, andultrasonically bonds the bumps to the pads, in which the bonding toolhas basically a square pole shape and has side surfaces that are bentinward with respect to virtual flat surfaces between adjacent corners ofthe bonding tool.

When the bonding tool presses and ultrasonic oscillation is applied tothe semiconductor chip, the insulating adhesive overflows from the sidesof the semiconductor chip, and not from the corners of the semiconductorchip. The bonding tool has basically a square pole shape, and the sidesurfaces of the bonding tool are bent inward with respect to the virtualflat surfaces between the adjacent comers of the bonding tool. In thisconfiguration, the overflowing insulating adhesive cannot reach andstick to the bonding tool. Accordingly, there is no need to clean thebonding tool. Also, since the bonding tool is basically the square pole,the entire semiconductor chip including the corners can be evenlypressed by the bonding tool. Thus, no cracks occur in the semiconductorchip.

The present invention also provides a method of mounting a semiconductorchip to be mounted on a substrate by a bonding tool that presses thesemiconductor chip while an insulating adhesive is interposed betweenthe semiconductor chip provided with bumps and the substrate providedwith pads, and ultrasonically bonds the bumps to the pads, in which asheet having a larger friction coefficient with both the semiconductorchip and the bonding tool than a friction coefficient between thesemiconductor chip and the bonding tool is interposed between thesemiconductor chip and the bonding tool, thereby carrying out ultrasonicbonding.

Since the sheet interposed between the bonding tool and thesemiconductor chip has a larger friction coefficient with both thesemiconductor chip and the bonding tool than the friction coefficientbetween the semiconductor chip and the bonding tool, the energytransmission from the bonding tool to the semiconductor chip can becarried out at high efficiency, and the bonding of the bumps formed onthe semiconductor chip to the pads formed on the substrate can becompleted in a short period of time. Also, less deviation occurs in thelocation of the semiconductor chip.

The present invention also provides a semiconductor chip mounting devicecomprising a bonding tool that presses a semiconductor chip while aninsulating adhesive is interposed between a semiconductor chip providedwith bumps and a substrate provided with pads, and ultrasonically bondsthe bumps to the pads; and a means for moving and placing a sheetbetween the bonding tool and the semiconductor chip which exhibits agreater friction coefficient with both the semiconductor chip and thebonding tool than a friction coefficient between the semiconductor chipand the bonding tool.

Since the friction coefficients between the bonding tool and the sheetand between the sheet and the semiconductor chip are both greater thanthe friction coefficients between the bonding tool and the semiconductorchip, the energy transmission from the bonding tool to the semiconductorchip can be efficiently carried out by placing the sheet between thebonding tool and the semiconductor chip. Accordingly, the bonding of thebumps formed on the semiconductor chip to the pads formed on thesubstrate can be completed in a shorter period of time. Also, lessdeviation occurs in the location semiconductor chip.

The present invention further provides a substrate on which asemiconductor chip is to be mounted by ultrasonic bonding, comprisingpads each having a shape that is elongated in a direction of ultrasonicoscillation applied to the semiconductor chip.

When the bonding tool applies ultrasonic oscillation to thesemiconductor chip, the semiconductor chip tends to be displaced due tothe orientation of the bonding tool. In the above configuration,however, the bumps formed on the semiconductor chip do not move off thepads each having a shape elongated in the direction of the ultrasonicoscillation. Thus, defective bonding can be prevented between thesemiconductor chip and the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a conventional hard disk device;

FIG. 2 illustrates a head slider assembly in the hard disk device ofFIGS. 1A and 1B;

FIGS. 3A to 3C illustrate a conventional printed circuit board unit;

FIGS. 4A to 4C illustrate a method of producing a conventionalsemiconductor chip;

FIGS. 5A and 5B illustrate a first problem of the prior art;

FIGS. 6A and 6B illustrate a second problem of the prior art;

FIGS. 7A and 7B illustrate a fourth problem of the prior art;

FIG. 8 illustrates rectangular pads of the prior art;

FIG. 9A and 9B illustrate a head IC chip mounting device of a firstembodiment of the present invention;

FIG. 10 is a plan view of the arrangement of ultraviolet lamps shown inFIGS. 9A and 9B;

FIG. 11 is a flowchart of the procedures of manufacturing a head sliderassembly;

FIGS. 12A to 12D are timing charts of the operation of the chip mountingdevice of FIGS. 9A and 9B;

FIG. 13 illustrates a positioning step in the flowchart of FIG. 11;

FIG. 14 illustrates a pressing and ultraviolet ray irradiation step inthe flowchart of FIG. 11;

FIG. 15 illustrates a pressing, ultrasonic oscillation, and ultravioletray irradiation step in the flowchart of FIG. 11;

FIG. 16 illustrates a situation immediately after the pressing,ultrasonic oscillation, and ultraviolet ray irradiation step;

FIGS. 17A and 17B illustrate a part of the completed head sliderassembly by the procedures shown in FIG. 11;

FIGS. 18A and 18B illustrate a chip mounting device of a secondembodiment of the present invention;

FIGS. 19A and 19B illustrate a chip mounting device of a thirdembodiment of the present invention;

FIG. 20 illustrates the top end of a bonding tool show in FIGS. 19A and19B;

FIG. 21 illustrates a first modification of the bonding tool of FIG. 20;

FIG. 22 illustrates a second modification of the bonding tool of FIG.20;

FIGS. 23A and 23B illustrates a chip mounting device of a fourthembodiment of the present invention;

FIG. 24 illustrates a polyimide film supporting mechanism shown in FIGS.23A and 23B;

FIG. 25 is a flowchart of a method of manufacturing the head sliderassembly of FIG. 2 using the chip mounting device of FIGS. 23A and 23B;

FIGS. 26A to 26F are timing chart of the operation of the chip mountingdevice of FIGS. 23A and 23B;

FIG. 27 illustrates a situation after a chip positioning step in theprocedures of FIG. 25;

FIG. 28 illustrates a temporary placing step in the procedures of FIG.25;

FIG. 29 illustrates a bonding tool lifting step in the procedures ofFIG. 25;

FIG. 30 illustrates a polyimide film interposing step in the proceduresof FIG. 25;

FIG. 31 illustrates a pressing and ultrasonic oscillation step in theprocedures of FIG. 25;

FIG. 32 illustrates a bonding tool lifting and polyimide film supportingmechanism retracting step in the procedures of FIG. 25;

FIGS. 33A and 33B illustrate a polyimide film feeding step in theprocedures of FIG. 25;

FIGS. 34A to 34D illustrates a head slider assembly of a fifthembodiment of the present invention;

FIGS. 35A to 35H illustrate the production procedures of Au pads shownin FIGS. 34A to 34D;

FIGS. 36A to 36G illustrate the production procedures continued fromFIG. 35H; and

FIGS. 37A and 37B illustrate a head slider assembly of a sixthembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment solves the problem that the shape of the fillet ofthe underfill is insecure.

FIGS. 9A and 9B show a head IC chip mounting device 100 as a firstembodiment of the present invention. The head IC chip mounting device100 comprises a stage 101, a bonding unit 110, and a control unit 130.

The stage 101 accommodates the suspension 12 shown in FIG. 2, and isprovided with suction holes 102 for sucking and attracting thesuspension 12. Also on the stage 101, four ultraviolet lamps 104 to 107surround a chip mounting position 109, and face the four sides of amounted head IC chip 11 so as to irradiate all the four sides of thehead IC chip 11 with ultraviolet rays.

The bonding unit 110 comprises a bonding head 111, a bonding tool 112hanging from the bonding head 111, and an ultrasonic oscillator 113integrally formed with the bonding tool 112. The bonding tool 112 ismoved up and down by an elevating mechanism (not shown). The bondingunit 110 is movably supported by a frame 103 of the head IC chipmounting device 100, and is moved by a moving mechanism (not shown).

The bonding head 111 contains a load cell (a pressing mechanism) 114 anda valve 115 that are connected to a power source or a vacuum source (notshown). The load cell 114 moves the bonding tool 112 up and down, andmeasures a force to be applied to a head IC chip 50 via the bonding tool112.

The bonding tool 112 is provided with a suction hole 116 thatcommunicates with the valve 115. The ultrasonic oscillator 113 providesultrasonic oscillation to the bonding tool 112.

The control unit 130 comprises a controller 131 that controls theultrasonic oscillator 113, a controller 132 that controls the load cell114, and a controller 133 that control the valve 115, and a controller134 that controls the ultraviolet lamps 104 to 107. The control unit 130further comprises an integrated controller 135 that controls all thecontrollers 131 to 134.

Referring now to FIG. 11, a method of manufacturing the head sliderassembly 19 of FIG. 2 using the above head IC chip mounting device 100will be described below.

The head slider assembly 19 is produced by carrying out steps 140 to 147shown in FIG. 11. Among steps 140 to 147, steps 144 to 146 are carriedout by the head IC chip mounting device 100 operating as shown in FIGS.12A to 12D.

Step 140

The Au bumps 51 are formed on the lower surface of the head IC chip 11using a wire bonding device.

Steps 141, 142, and 143

The Au pads 61 are formed on the suspension 12, and adhesive 150 to bethe underfill is applied to the center of the chip mounting position109. With the AU pads 61 and the adhesive 150 facing upward, thesuspension 12 is placed on the stage 101, and is sucked to adhere ontothe stage 101.

The adhesive 150 consists of a mixture of thermosetting adhesive and anultraviolet curing agent. More specifically, the adhesive 150 consistsof urethane acrylate resin as a main component, benzoin alkyl ether as aphotoinitiator for polymerization, and acrylate as a thermosettinginitiator.

Positioning Step 144 (see FIGS. 13 and 12A)

The bonding unit 110 is located at the aligning position of head ICchips 11. The bonding tool 112 is moved down by an elevating mechanism(not shown). As shown in FIG. 12A, the valve 115 is opened in accordancewith a control signal transmitted from the controller 133. One of thehead IC chips 11 is vacuum-sucked by the top end of the bonding tool112. The bonding tool 112 then moves up to lift up the head IC chip 11.Successively, the bonding unit 110 is moved along the frame 103 by amoving mechanism (not shown) so as to transport the head IC chip 11. Thebonding unit 110 is then stopped at such a position that the head ICchip 11 is positioned to the suspension 12, as shown in FIG. 13.

Pressing and Ultraviolet Ray Irradiation Step 145 (FIGS. 14, 12B, and12C)

As the elevating mechanism (not shown) is actuated, the load cell 114operates in accordance with a control signal transmitted from thecontroller 132, as shown in FIG. 12C. The bonding tool 112 is then moveddown to pressurize the head IC chip 11 with a predetermined force F,thereby pressing the AU bumps 51 toward the Au pads 61. The head IC chip11 also spreads out the adhesive 150 by the force F. Here, the adhesive150 is spread out to such an extent that the edge of the adhesive 150overflows out of the rim of the head IC chip 11. In FIG. 14, referencenumeral 151 indicates the adhesive spread out on the suspension 12 bythe head IC chip 11.

When the load cell 114 starts pressurizing the head IC chip 11, theultraviolet lamps 104 to 107 are switched on in accordance with acontrol signal transmitted from the controller 134. The area surroundingthe head IC chip 11 is irradiated with ultraviolet rays 108, and theportion 151 a of the adhesive 151 exposed out of the rim of the head ICchip 11 starts hardening. Accordingly, the spread-out adhesive 151 ispartially hardened. In FIG. 14, reference numeral 152 indicates thehardened portion.

In the above manner, the portion 151 a of the adhesive 151 exposed outof the rim of the head IC chip 11 is hardened so that a rigid film isformed at the exposed portion 151 a. Accordingly, when the head IC chip11 is pressed against the suspension 12, the adhesive 151 is preventedfrom flowing out of the suspension 12.

The ultraviolet rays 108 do not reach the bottom of the head IC chip 11.Accordingly, the portion of the adhesive 151 under the head IC chip 11has not hardened at this point. Thus, the adhesive 150 can be smoothlyspread out when the head IC chip 11 is pressed, and the Au bumps 51 canbe accurately pressed against the Au pads 61.

Pressing, Ultrasonic Oscillation, and Ultraviolet Ray Irradiation Step146 (see FIGS. 15, 16, 12A, 12B, 12C, and 12D)

As shown in FIGS. 12A, 12B, and 12C, the ultraviolet lamps 104 to 107are on, the bonding tool 112 vacuum-sucks the head IC chip 11, and theload cell 114 presses the head IC chip 11. Under this condition, theultrasonic oscillator 113 starts oscillating in accordance with acontrol signal transmitted from the controller 131, and keepsoscillating for several seconds.

FIG. 15 illustrates the above situation. When the ultrasonic oscillator113 oscillates, the bonding tool 112 ultrasonically oscillates asindicated by the arrow B. The ultrasonic oscillation of the bonding tool112 is transmitted to the Au bumps 51 of the head IC chip 11, and the Aubumps 51 ultrasonically oscillate against the Au pads 61. Thus, the Aubumps 51 are bonded to the Au pads 61.

The portion 151 a of the adhesive 151 exposed out of the rim of the headIC chip 11 is further hardened. In FIG. 15, reference numeral 153indicates the further-hardened portion. Since the portion 151 a exposedout of the rim of the head IC chip 11 is hardened, the adhesive 151 canbe prevented from flowing out of the suspension 12 when the head IC chip11 ultrasonically oscillates. Also, the adhesive 151 can be preventedfrom entering the contact portion between the bonding tool 112 and thehead IC chip 11. Thus, a preferable contact condition can be maintainedbetween the bonding tool 112 and the head IC chip 11.

The ultraviolet rays 108 do not enter the bottom of the head IC chip 11.Accordingly, the portion of the adhesive 151 situated below the head ICchip 11 has not been hardened at this point. The Au bumps 51 areproperly pressed against the Au pads 61. Thus, the bonding conditionbetween the Au bumps 51 and the Au pads 61 can be desirably maintained.

FIG. 16 illustrates a situation immediately after the pressing,ultrasonic oscillation, and ultraviolet ray irradiation step 146. Theultraviolet lamps 104 to 107 are switched off, and the Au bumps 51 arebonded to the Au pads 61. The adhesive 151 fills the small space 152between the lower surface of the head IC chip 11 and the upper surfaceof the suspension 12, and only the portion 151 a exposed out of the rimof the head IC chip 11 has been hardened.

Heating Step 147

The suspension 12, to which the head IC chip 11 is bonded, is taken outof the chip mounting device 100, The suspension 12 is then placed into aheating furnace to thermally harden the adhesive 151. At this point, theentire adhesive 151 is completely hardened to form an underfill 155.

Through the above steps, a head slider assembly 19A shown in FIGS. 17Aand 17B are completed. The Au bumps 22 formed on the lower surface ofthe head IC chip 11 are bonded to the Au pads 61 on the suspension 12.The head IC chip 11 is also bonded to the suspension by the underfill155, which is formed by hardening the ultraviolet curing andthermosetting adhesive 150. The underfill 155 has a desirable fillet 156on its entire peripheral portion. Since the adhesive 150 is appliedfirst, the underfill 155 has high quality without voids.

A second embodiment of the present invention is a modification of thefirst embodiment, and solves the problem that the shape of the fillet ofthe underfill may vary.

FIGS. 18A and 18B illustrate a chip mounting device 100 of the secondembodiment of the present invention. The chip mounting device 100A isprovided with heaters 164 to 167 in place of the ultraviolet lamps 104to 107 of the chip mounting device 100 shown in FIGS. 9A and 9B. Theheaters 164 to 167 surround the chip mounting position 109, and arearranged so as to irradiate all the sides of the head IC chip 11 withthermal rays 168.

As for the adhesive, thermosetting adhesive 150A is used.

When the head IC chip 11 is pressed against the suspension 12 and whenthe head IC chip 11 is subjected to an ultrasonic wave, the heaters 164to 167 are switched on to irradiate the portion 151 a of thethermosetting adhesive 150A exposed out of the rim of the head IC chip11 with the thermal rays 168, thereby hardening the exposed portion15la. Thus, the adhesive 150A can be prevented from flowing out of thesuspension 12, and an excellent fillet 156 can be formed.

Third, fourth and fifth embodiments solve the problem that theoverflowing adhesive sticks to the bonding tool.

FIGS. 19A and 19B illustrate a chip mounting device 100B of the thirdembodiment of the present invention. The chip mounting device 100B doesnot include the ultraviolet lamps 104 to 107 and the controller 134 ofthe chip mounting device 100 shown in FIGS. 9A and 9B, and is providedwith a bonding tool 112C shown in FIG. 20 instead of the bonding tool112.

The bonding tool 112C is made of stainless steel, and takes the form ofa pillar. The section of the bonding tool 112C has a square shapecorresponding to the shape of the head IC chip 11. Also, the bondingtool 112C is the same size as the conventional bonding tool 112. Thebonding tool 112C differs from the bonding tool 112 in that it hasV-shaped sides. In other words, the bonding tool 112C is basically asquare pole having four V-shaped side surfaces 112Ca to 112Cd and fourcorners 112Ce to 112Ch. The side surfaces 112Ca to 112Cd are bent inwardwith respect to the virtual flat surfaces between every two adjacentcomers of the comers 112Ce to 112Ch.

As shown in FIG. 19A, the bonding tool 112C sucks the head IC chip 11 sothat the heat IC chip 11 presses against the suspension 12, with thecomers 112Ce to 112Ch corresponding to the corners 11 a of the head ICchip 11. The side surfaces 112Ca to 112Cd of the bonding tool 112C arebent toward the center of the head IC chip 11 with respect to the sides11 b of the head IC chip 11.

When the head IC chip 11 is pressed by the bonding tool 112C, adhesive150C might overflow onto the upper surface of the head IC chip 11 fromunderneath. In FIGS. 19A and 19B, the overflowing portion of theadhesive 150C is indicated by reference numeral 150Ca. The appliedadhesive 150C is circular in shape when seen from above, and theoverflowing portion should be radially spread. Accordingly, theoverflowing portion 150Ca of the adhesive 150C on the upper surface ofthe head IC chip 11 is situated on the sides 11 b of the head IC chip11.

Since the side surfaces 112Ca to 112Cd of the bonding tool 112C are benttoward the center of the head IC chip 11, the overflowing portion 150Caof the adhesive 150C does not stick to the side surfaces 112Ca to 112Cdof the bonding tool 112C. Accordingly, the top end of the bonding tool112C is always kept clean, and there is no need to take trouble to cleanthe top end of the bonding tool 112C every time the mounting of one headIC chip 11 is completed.

To prevent the overflowing portion of the adhesive on the upper surfaceof the head IC chip 11 from sticking to the top end of the bonding tool,it is also possible to form the top end of the bonding tool into asquare shape and make the bonding tool much smaller than the head ICchip 11. In that case, however, the bonding tool presses the center ofthe head IC chip 11, and the pressure of the bonding tool concentrateson the center of the head IC chip 11. As a result, cracks will occur inthe head IC chip 11.

Since the bonding tool 112C is substantially the same size as theconventional bonding tool 112, the four corners 112Ce to 112Ch pressesthe neighboring areas of the corners 11 a of the head IC chip 11.Accordingly, as with the conventional bonding tool 112, the bonding tool112C presses the entire upper surface of the head IC chip 11, so that nocracks occur in the head IC chip 11.

Instead of the bonding tool 112C shown in FIG. 20, a bonding tool 112Dshown in FIG. 21 or a bonding tool 112E shown in FIG. 22 can beemployed.

The bonding tool 112D shown in FIG. 21 has four corners 112De to 112Dhand four curved side surfaces 112Da to 112Dd. The side surfaces 112Da to112Dd are bent inward with respect to the virtual flat surfaces betweenthe adjacent comers 112De to 112Dh.

The bonding tool 112E has four corners 112Ee to 112Eh and four curvedside surfaces 112Ea to 112Ed. The side surfaces 112Ea to 112Ed are bentinward with respect to the virtual flat surfaces between the adjacentcorners 112Ee to 112Eh.

With either the bonding tool 112D shown in FIG. 21 or the bonding tool112E shown in FIG. 22, the same effects can be obtained as with thebonding tool 112C shown in FIG. 20.

A fourth embodiment of the present invention solves the problem that theconductivity of ultrasonic waves from the tool to the head IC chip islow.

FIGS. 23A and 23B show a chip mounting device 100F of the fourthembodiment of the present invention. The chip mounting device 100F isprovided with a polyimide film supporting mechanism 170 on the stage101, instead of the ultraviolet lamps 104 to 107 of the chip mountingdevice 100 shown in FIGS. 9A and 9B. In FIGS. 23A and 23B, the samecomponents as in FIGS. 9A and 9B are indicated by the same referencenumerals, and the descriptions for those components are omitted. Thewidth direction of the chip mounting device 100F are indicated by X1 andX2, and the depth direction of the chip mounting device 100F areindicated by Z1 and Z2.

As shown in FIG. 24, the polyimide film supporting mechanism 170comprises a U-shaped frame 172, a feeding roller supporting member 174that is disposed at the X1 side of the frame 172 and supports a feedingroller 173 for feeding tape-type polyimide film 171, and a windingroller supporting member 174 that is disposed at the X2 side of theframe 172 and supports a motor 175 and a winding roller 176. TheU-shaped frame 172 is movable along guide rails 178 and 179 on the stage101 in the Y1-Y2 directions. A moving mechanism 181 containing a motor180 moves the frame 172 between an interposing position P1 below thebonding tool 112 and a retracting position P2 shifted from theinterposing position P1 in the Y2 direction. The tape-type polyimidefilm 171 horizontally extends between the feeding roller 173 and thewinding roller 176 at the same height P3 as the upper surface of themounted head IC chip 11.

A control unit 130F comprises a controller 190 for controlling the motor180 and a controller 191 for controlling the motor 175, instead of thecontroller 134 shown in FIG. 9B.

Referring now to FIG. 25, a method of manufacturing the head sliderassembly 19 of FIG. 2 using the above chip mounting device 100F will bedescribed below.

The head slider assembly 19 is manufactured by carrying out steps 140 to144, 147, and 200 to 205. Among those steps 140 to 144, 147, and 200 to205, steps 144 and 200 to 205 are carried out by the chip mountingdevice 100F operating as shown in FIGS. 26A to 26F.

The polyimide film supporting mechanism 170 is located at the retractingposition P2 shown in FIGS. 23B and 24. Steps 140 to 144 are carried outin the same manner as in the procedures shown in FIG. 11.

FIG. 27 illustrates a situation after the positioning step 144. In FIG.27, the top end of the bonding tool 112 vacuum-sucks one head IC chip11, and stops at a predetermined position so that the head IC chip 11 ispositioned to the suspension 12 fixed onto the stage 101.

Temporary Placing Step 200 (see FIGS. 28, 26A, and 26B)

As an elevating mechanism (not shown) is actuated, the bonding tool 112is moved down so that the head IC chip 11 spreads out the adhesive 150.Accordingly, the head IC chip 11 is positioned and bonded to thesuspension 12 by the adhesive 150. Thus, the head IC chip 11 istemporarily placed on the suspension 12.

Bonding Tool Lifting Step 201 (see FIGS. 29, 26A, and 26B)

As shown in FIG. 26A, the valve 115 is closed to stop the vacuumsuction. As shown in FIGS. 28 and 26B, the bonding tool 112 is movedupward by the elevating mechanism (not shown), leaving the head IC chip11 on the suspension 12.

Polyimide Film Interposing Step 202 (see FIGS. 30 and 26C)

As shown in FIG. 26C, the motor 180 is driven by the controller 190, andthe polyimide film supporting mechanism 170 is moved in the Y Idirection by the moving mechanism 181. The polyimide film supportingmechanism 170 is moved to the interposing position PI as shown in FIG.30, so that the polyimide film 171 covers the head IC chip 11.

Pressing and ultrasonic oscillation Step 203 (see FIGS. 31, 26D, and26E)

As the elevating mechanism (not shown) is actuated, the bonding tool 12is moved down as shown in FIG. 26B. The load cell 114 operates as shownin FIG. 26D, in accordance with a control signal transmitted from thecontroller 132. As shown in FIG. 31, the lowered bonding tool 112presses the head IC chip 11 by a predetermined force F via the polyimidefilm 171, so as to press the Au bumps 51 against the Au pads 61.

As shown in FIG. 26E, the ultrasonic oscillator 113 starts oscillatingin accordance with a control signal transmitted from the controller 131,and the ultrasonic oscillator 113 keeps oscillating for several seconds.With the ultrasonic oscillator 113 oscillating, the bonding tool 112ultrasonically oscillates in the directions of the arrow B as shown inFIG. 31. The ultrasonic oscillation of the bonding tool 112 istransmitted to the Au bumps 51 on the head IC chip 11 via the polyimidefilm 171. The Au bumps 51 in turn ultrasonically oscillate against theAu pads 61. Thus, the Au bumps 51 are bonded to the Au pads 61.

The friction coefficient μ10 between the stainless bonding tool 112 andthe polyimide film 171 is in the range of 1 to 4, and the frictioncoefficient μ11 between the polyimide film 171 and the silicon head ICchip 11 is also in the range of 1 to 4. These friction coefficients μ10and μ11 are greater than the friction coefficient μ1 between the tool 75and the head IC chip 11. Accordingly, the transmission of ultrasonicwaves from the bonding tool 112 to the head IC chip 11 can be carriedout at a higher efficiency than in the prior art, and the bonding of theAu bumps 51 to the Au pads 61 can be completed in a shorter period oftime than in the prior art.

Bonding Tool Lifting and Polyimide Film Supporting Mechanism RetractingStep 204 (see FIGS. 32, 26B, and 26C)

As the elevating mechanism (not shown) is actuated as shown in FIG. 26B,the bonding tool 112 is moved up, as shown in FIG. 32. As shown in FIG.26C, the motor 180 is driven by the controller 190, and the polyimidefilm supporting mechanism 170 is moved in the Y2 direction by the movingmechanism 181. The polyimide film supporting mechanism 170 is moved backto the retracting position P2 as shown in FIG. 32, and the polyimidefilm 171 retracts from the head IC chip 11, leaving the head IC chip 11in the exposed state.

Heating Step 147

The suspension 12, to which the head IC chip 11 is bonded, is taken outof the chip mounting device 110F, and placed into a heating furnace asshown in FIG. 4C. In the heating furnace, the entire adhesive 151 isthermally hardened. Thus, the head slider assembly 19A shown in FIGS.17A and 17B is completed.

The adhesive 151 is turned into the underfill 155. The Au bumps 51formed on the lower surface of the head IC chip 11 is bonded to the Aupads 61 on the suspension 12. The head IC chip 11 is bonded onto thesuspension 12 by the underfill 155 formed by hardening the ultravioletcuring and thermosetting adhesive 150.

Polyimide Film Feeding Step 205 (see FIGS. 33A, 33B, and 26F)

As shown in FIG. 26F, the motor 175 is driven in accordance with asignal transmitted from the controller 191. As shown in FIGS. 33A and33B, the winding roller 176 winds up the tape-type polyimide film 171 inthe direction of the arrow E. The polyimide film 171 is then sent out inthe X2 direction from the feeding roller 173. The tape-type polyimidefilm 171 is moved in the X2 direction by a length equivalent to thelength of each side of the head IC chip 11. Thus, new polyimide film forthe mounting of the next head IC chip is prepared.

In the above manner, the operation of the chip mounting device 100F iscompleted. In the above procedures, the pressing ultrasonic oscillationstep 203 requires a shorter period of time than in the prior art.Accordingly, the head slider assembly can be manufactured at higherworkability than in the prior art.

Since the bonding tool 112 applies a load and ultrasonic oscillation tothe head IC chip 11 via the polyimide film 171 as shown in FIG. 31, thefollowing two incidental effects can be attained:

1. Since the polyimide film 171 pressed by the bonding tool 112 consistsof synthetic resin, the upper surface of the polyimide film 171 isdeformed by the minute concavities and convexities of the end surface ofthe bonding tool 112. As a result, the end surface of the bonding tool112 firmly adheres to the upper surface of the polyimide film 171. Thus,the orientation of the end surface of the bonding tool 112 can beeliminated. The lower surface of the polyimide film also firmly adheresto the upper surface of the head IC chip 11. When the bonding tool 112ultrasonically oscillates, the head IC chip 11 returns to the originalposition from a displaced point. Thus, no deviation occurs in theposition of head IC chip 11.

2. The polyimide film 171, that covers the upper surface of the head ICchip 11, prevents the overflowing adhesive from flowing onto the uppersurface of the head IC chip 11.

A fifth embodiment of the present invention solves the problem thatdeviation of the head IC chip might result in defective mounting.

FIGS. 34A to 34D illustrate a head slider assembly 19G of the fifthembodiment of the present invention. The head slider assembly 19Gpositions the head IC chip 11 to a suspension 12G, as in the foregoingembodiments, and the bonding tool 112 applies a load and ultrasonicoscillation to the head IC chip 11. By doing so, the Au bumps 51 arebonded to Au pads 61G on the suspension 12G, and the head IC chip 11 isbonded to the suspension 12G by the hardened underfill 155.

Each of the Au pads 61 G has a length L20 in the direction of ultrasonicoscillation B (the X1-X2 direction) generated by the bonding tool 112and a length L21 in the direction perpendicular to the direction of theultrasonic oscillation B. The length L20 is four times as long as thelength 21. Accordingly, each Au pad 61 G is elongated in the directionof the ultrasonic oscillation B.

FIGS. 34A and 34B show the head IC chip 11 positioned onto thesuspension 12G. Each of the Au bumps 51 is in contact with the center ofeach corresponding Au pad 61G. Since the end surface 112 a of thebonding tool 112 has a little orientation, the head IC chip 11 isslightly deviated from the original position shown in FIGS. 34A and 34Bin one direction of the ultrasonic oscillation (in the X1 direction, forinstance) every time the bonding tool 112 ultrasonically oscillates.However, the Au pads 61G, which are elongated in the direction of theultrasonic oscillation B applied by the bonding tool 112, prevent therespective Au bumps 51 from deviating from the respective Au pads 61.Thus, the Au bumps 51 are properly bonded to the Au pads 61G.

Instead of the bonding tool 112, any of the bonding tools 112C, 112D,and 112E shown in FIGS. 20 to 22 can be employed.

The long Au pads 61G are produced as shown in FIGS. 35A to 35H and 36Ato 36D.

First, as shown in FIGS. 35A and 35B, copper foil 211 is bonded to theupper surface of a suspension base member 210 made of stainless steel,thereby forming a copper-foiled suspension 212. Next, a photoresist film213 is formed on the copper-foiled suspension 212, as shown in FIGS. 35Cand D. A photomask 214 provided with windows 214 a having the same shapeas the long Au pads 61G is positioned onto the photoresist film 213, asshown in FIGS. 35E and 35F. A light source 215 then exposes thesuspension 212, as shown in FIGS. 35G and 35H, so as to harden thephotoresist film 213. Next, photoresist-etching is performed to leavephotoresist portions 213 a, as shown in FIGS. 36A and 36B. The copperfoil 211 is also etched as shown in FIGS. 36C and 36D, and thephotoresist portions 213 a are removed as shown in FIGS. 36E and 36F.Thus, the long Au pads 61G are formed on the suspension base member 210.

A sixth embodiment of the present invention solves the same problemsolved by the fifth embodiment.

FIG. 37B illustrates a head slider assembly 19H of the sixth embodimentof the present invention. The head slider assembly 19H comprises a headIC chip 11H. This head IC chip 11H has Au bumps 51H arranged along thefour sides. For ease of drawing, the outline of the head IC chip 11H andthe outline of the bonding tool 112 are indicated by two-dot chainlines. As shown in FIG. 37A, the head slider assembly 19H positions thehead IC chip 11H onto a suspension 12H. The bonding tool 112 thenapplies a load and ultrasonic oscillation to the head IC chip 11H, sothat the Au bumps 51H are bonded to Au pads 61H on the suspension 12H,and that the head IC chip 11H is bonded to the suspension 12H by thehardened underfill (not shown).

In conformity with the structure of the Au bumps 51H attached to thehead IC chip 11H, the Au pads 61H on the suspension 12H are arrangedalong the four side of the square. The Au pads 16H each have the sameshape as the Au pads 61G shown in FIGS. 34A to 34D. The Au bumps 51H hasa longitudinal direction V1-V2 between the X1 direction and the Y1direction, which is equivalent to an axis line X1-X2 rotatedcounterclockwise at an angle of 45 degrees. In this arrangement, the Aubumps 51H can be prevented from interfering with each other. Also, thebonding tool 112 is designed to oscillate ultrasonically in the V1-V2direction.

Due to the slight orientation of the end surface of the bonding tool112, the head IC chip 11H is slightly deviated from the initial positionshown in FIG. 37A in one oscillating direction (in the V1 direction, forinstance) every time the bonding tool 112 ultrasonically oscillates.However, the Au bumps 51H do not separate from the Au pads 61H. andremains on the Au pads 61. Thus, the Au bumps 51H can be properly bondedto the Au pads 61H.

Instead of the bonding tool 112, any of the bonding tools 112C, 112D,and 112E, shown in FIGS. 20, 21, and 22, can be employed.

It should be noted that the present invention can be applied not only tothe head slider assembly described above, but also to the mounting ofthe IC chip 31 on the substrate 32 in the multi chip module 36 of theprinted circuit board unit 30 shown in FIG. 3.

What is claimed is:
 1. A method of mounting a semiconductor chip to asubstrate, comprising the steps of: bonding bumps formed on thesemiconductor chip to pads formed on the substrate by pressing thesemiconductor chip, with insulating adhesive being interposed betweenthe semiconductor chip and the substrate; and hardening the insulatingadhesive spread out between the semiconductor chip and the substrate,wherein the bonding step includes the step of hardening a peripheralportion of the insulating adhesive spread out between the semiconductorchip and the substrate before a center portion of the insulativeadhesive is hardened.
 2. The method of mounting a semiconductor chip toa substrate as claimed in claim 1, wherein the bonding step furtherincludes the step of applying ultrasonic oscillation to thesemiconductor chip so that the bumps formed on the semiconductor chipare bonded to the pads formed on the substrate.
 3. The method ofmounting a semiconductor chip to a substrate as claimed in claim 1,wherein the peripheral portion of the insulating adhesive is hardened byone of light and heat.
 4. A method of mounting a semiconductor chip tobe mounted on a substrate by a bonding tool, comprising the steps of:pressing the semiconductor chip while an insulating adhesive isinterposed between the semiconductor chip provided with bumps and thesubstrate provided with pads, and ultrasonically bonding the bumps tothe pads, wherein a sheet having a greater friction coefficient with thesemiconductor chip and the bonding tool than a friction coefficientbetween the semiconductor chip and the bonding tool is interposedbetween the semiconductor chip and the bonding tool, thereby carryingout ultrasonic bonding.